1. Field of the Invention
The present invention relates to a valve assembly which is attached to a gas cylinder for storing compressed gas and liquefied gas.
2. Explanation of Related Art
There is a conventional example of the valve assembly with a check valve of this type, disclosed in Japanese Utility Model Publication No. 56-50234 proposed earlier by an Assignee of the present invention.
The conventional example comprises a housing within which an inlet bore communicates with an outlet bore through a shut off valve chamber, a check valve seat and a check valve chamber in the mentioned order. A check spring resiliently pushes for valve closing, a check valve member inserted into the check valve chamber to the check valve seat. The check valve member is formed with a cavity for valve opening, which is opposed to the outlet bore.
And when charging new gas into a gas cylinder, a valve opening means provided at a leading end of a gas charging mouthpiece is hermetically fitted into the cavity and a pressure of the charging gas separates the check valve member from the check valve seat.
The conventional technique can forcedly open the check valve with the pressure of the charging gas. Further, the check valve member can be opened or cancelled from being opened at the same time as the gas charging mouthpiece is attached to or detached from an outlet nozzle of the valve assembly. Therefore, it is excellent because of easiness in operation during the gas charging. However, the conventional technique has to be still improved on the following points.
(1) It takes lots of time to effect the gas charging.
Since the gas charging mouthpiece is inserted into the outlet bore having a narrow and limited size, a gas charging passage within the leading end portion of the mouthpiece cannot help having a reduced flow passage sectional area. Besides, it is necessary to make a hermetically sealing and sliding portion of the cavity provided in the check valve member larger than a valve face of the check valve member in sectional area. Therefore, the valve opening means cannot help but have an increased outer diameter. In addition, a flow passage sectional area is reduced between an inner peripheral surface of the outlet bore and an outer peripheral surface of the valve opening means. As such, at the time of charging gas, the flow passage sectional area is so small that it takes a long time to charge the gas. In the case where the gas to be charged is liquefied gas, this problem appears as a more remarkable disadvantage because flow resistance becomes larger.
(2) Low workability at the time of effecting the gas charging.
As the check valve becomes smaller, it is harder to hermetically fit into the cavity the valve opening means provided at the leading end of the gas charging mouthpiece. Further, there is a necessity of interposing an O-ring or the like sealing means in a space defined between the hermetically sealing and sliding surface of the cavity and the outer peripheral surface of the valve opening means. However, if this sealing means is damaged because of biting dust and the like foreign matters and so on, it causes an erroneous valve opening with the result of decreasing the working efficiency at the time of charging gas.
(3) It is impossible to reduce a diameter of a connecting threaded portion which is formed in the outlet nozzle.
The valve opening means has to be inserted into the outlet bore. Therefore, the outlet nozzle cannot help but increase its outer diameter. This results in the problem of being able to put into practice only the threaded portion of large diameter for the connecting one which is formed in an outer periphery of the outlet nozzle.